The present invention relates in general to communication systems and components therefor, and is particularly directed to a new and improved phased array antenna architecture, formed by a stacked arrangement of tray-configured modules containing signal processing and routing networks having mutually orthogonal spatial configurations, that facilitate integrating all of the components of the antenna in a highly densified package, that not only reduces occupied volume, but provides for direct low loss ribbon bonding between signal components and microstrip conductors of associated signal distribution networks.
Among desired characteristics of multi-element antenna systems (e.g., phased array antennas) of the type that may be deployed on a mobile platform, such as a satellite, are the requirement that the antenna be physically compact, while also being sufficiently broadband to meet performance requirements of terrestrial communication systems. Indeed, the on-going trend is towards deploying systems capable of producing multiple independent steerable beams operating at higher frequencies (such as those operating at 25-40 GHz and above). Although progress has been made in reducing the physical size and packaging density of the radiating elements, per se, the substantial physical space required to implement and mount their associated control networks and interconnection circuitry has effectively limited the size and packaging density of the total system.
This problem becomes acute in multi-beam applications, which require very high RF distribution, with each beam having its own set of beam steering and combining components installed behind a shared aperture. At Ka-band, for example, providing an interconnect architecture between the antenna""s beam forming network and the antenna modules becomes a particularly daunting challenge, as a fully periodic wide scan multibeam array requires a very densely packed array of very small geometry antenna elements, for which a very large number of electrical connections are required.
Pursuant to the present invention, these requirements are satisfied by a new and improved, extremely compact, phased array antenna architecture used for very high frequency, multi-beam applications, that successfully integrates a plurality of closely spaced antenna elements of a generally planar spatial array with associated amplifier, phase shift and power divider and distribution networks, in a highly nested physical structure. As will be described, this highly nested structure relies upon the mutual orthogonality of the layout and configuration of each of its components, that enable it to enjoy a significantly reduced size and packaging density in contrast to prior art systems.
To this end, the multi-beam phased array antenna architecture of the invention is assembled by stacking together a plurality of relatively thin, generally flat or planar, tray-configured, multi-antenna element support and control modules. Mutually adjacent top edges of the modules of the stack contain sets or rows of plural antenna elements per row. The number of antenna elements in a given row and thereby the resulting two dimensional distribution for the stack is based upon the intended spatial geometry characteristics of the overall array. The modules are retained in side-by-side, edge-adjacent relationship by a generally rectangularly shaped frame, that also retains power supply and control electronics modules for the array.
Opposite sides of a support member for a respective antenna module are preferably mirror images of one another, each being configured as a generally rectangular tray-shaped structure. The top edge of the tray-shaped support member of a respective antenna module serves as a support surface for a portion of (e.g., two parallel rows of) the antenna elements of the phased array, and includes conductive, xe2x80x98coaxial-likexe2x80x99 vias for connecting the antenna elements installed in the two rows with associated electronic circuit components (e.g., antenna amplifier circuits) installed on opposite sides of the tray. A front edge of the tray, adjacent to the top edge, has a set of mesas, bores through which contain signal connectors configured to be interconnected or plugged with associated connectors of externally accessible signal combiner network modules, outputs of which are associated with respective beams of the multi-beam array.
Each side of a respective antenna module""s generally rectangular tray-shaped structure is configured to accommodate power supply and control electronic circuit components. It also has a recessed floor region containing longitudinal depressions that extend in parallel along a first (e.g., xe2x80x98verticalxe2x80x99) direction from locations adjacent to the antenna amplifier modules of the device-mounting region. These longitudinal depressions are sized to accommodate respective ones of generally xe2x80x98verticallyxe2x80x99 oriented microstrip layers on the xe2x80x98undersidexe2x80x99 of a double-sided printed wiring board, as mounted in a face-down orientation against the recessed floor region.
The number of vertical microstrip traces along the underside of a double-sided printed wiring board corresponds to the maximum number of antenna elements that may be accommodated in a respective row on the top edge of the module. The outputs of the antenna amplifier modules are coupled (e.g., ribbon bonded) to (terminal end pads of) respective ones of the generally xe2x80x98verticallyxe2x80x99 oriented microstrip layers, with the depressions in the tray providing electrical shielding for the vertical microstrip conductors.
The double-sided printed wiring board, which is a relatively low loss structure and facilitates interconnects, comprises a laminate of a ground plane (e.g., metallic) layer and a pair of xe2x80x98undersidexe2x80x99 and xe2x80x98topsidexe2x80x99 dielectric layers containing patterned mutually orthogonal or xe2x80x98horizontalxe2x80x99 microstrip layers. The topside dielectric layer is patterned into parallel xe2x80x98horizontalxe2x80x99 stripe-shaped sections, on which xe2x80x98horizontalxe2x80x99 microstrip layers extend in a direction orthogonal to the xe2x80x98verticalxe2x80x99 microstrip layers on the underside of the double-sided printed wiring board. The number of horizontal microstrip layers on the topside of the double-sided printed wiring board corresponds to the number of beams formed by the multi-beam phased array antenna.
Since each of the antenna elements on the top edges of the stacked modules is associated with the generation of each of the multi-beams of the phased array, it is necessary to provide a respective phase shifterxe2x80x94per antenna elementxe2x80x94per beam. For this purpose, the double-sided printed wiring board contains conductive vias, which connect plural signal distribution (power divider) locations (corresponding to the number of beams) along the vertical microstrip layers on the underside of the board to locations for effecting connections to respectively associated phase shift modules installed in module mounting regions adjacent to the horizontal microstrip layers on the topside of the double-sided printed wiring board.
For this purpose, the stripe-shaped sections of dielectric, on which the horizontal microstrip layers are distributed, are spaced apart by phase shifter module-mounting regions that are sized to accommodate placement of the phase shift modules, so that their terminal pads are immediately adjacent to the connection vias and phase shifter module connection locations of the horizontal microstrip layers. This immediate proximity of terminal pads of the microstrip layers and electronic components and conductive vias of the orthogonally arranged microstrip layers of the printed wiring boards facilitates interconnections thereamong by the use of ribbon bonding, applied by robotically controlled equipment, and enables them to be impedance-matched at the very high operational frequencies of the antenna array.
The horizontal microstrip layers on the topside of the double-sided printed wiring board terminate at connection pads immediately adjacent to (module-installed) associated beam amplifier circuits mounted adjacent to the front edge of the board. The output of a respective beam""s amplifier circuit for each antenna module is coupled to an amplifier module connector installed in an associated one of the mesas at the front edge of the antenna module. These amplifier module connectors are connected, in turn, with respective beam-associated aconnectors of signal combiner network modules distributed along the front edges of the antenna modules as stacked in the support frame.
Each signal combiner network module contains input connector ports aligned with the connectors in the mesas of the plural antenna modules of the stack. The input connector ports are internally terminated to respective terminal pad locations of adjacent microstrip-configured, beam signal combiners, one for each of the beams of the multibeam array, so that a respective signal combiner of a beam signal combiner network module sums the contribution of each row of antenna elements of each antenna module across the entire stack for a given beam. Respective summing ends of the signal combiners are connected to associated summing amplifier modules, outputs of which are ported to beam terminal connectors, each of which is associated with a respectively different beam of the multi-beam array.